A Local Area Network (LAN) is a communication network which interconnects several computer or data terminals. Each of the computers or other devices is said to be located at a node or station of the network. The network allows the computers and/or terminals to communicate (receive and transmit information) with the other nodes of the LAN. Optical LANs are becoming more and more prevalent with the advent of technologies such as the Fiber Distributed Data Interface (FDDI). This technology employs fiber optics as the transmission medium, allowing transmission rates up to 100 Mbits per second.
As optical LANS become more common, the maintenance of the optical links connecting the nodes of the LAN will become increasingly important. Marginal optical links can inject undesirable errors into the data stream of a point to point communication link. While certain systems have a high tolerance for transmission media errors, many systems are unable to cope with such media difficulties. Burst errors, multiple errors within a relatively short period of time, can occur from conditions on the optical link of a fairly normal nature, such as extended marginal link quality, link degradation, or dirty connectors. Utility power grids are another source of noise which can cause bit errors in an optical link.
Unnecessary link terminations are the usual result of such noise bursts. Link termination requires the logical connection between FDDI nodes to cease, thus requiring the station to re-establish the logical connection if communication is to resume. The termination and re-establishment process can result in a significant decrease in system throughput and an increasing complex LAN management system. When the logical connection between two FDDI nodes is removed due to bursts of noise, the FDDI logical ring will be either temporarily wrapped, or a cluster of stations will be segmented. Clearly, it is desirable to avoid either of these situations. Present link management capabilities are incomplete and do not prevent these problems.
It is therefore one object of this invention to improve link management capabilities.
It is also an object of this invention to increase fault diagnostics and fault isolation capabilities while increasing system throughput.
It is another object of this invention to manage burst link errors without terminating link communications.